CodeSubmit Interview Series

The 9 Best Mobile Developer Interview Questions in 2023

What are the best mobile developer interview questions? Here are the top interview questions to ask at your next interview. Read on!

Interviewing mobile developers 

A mobile developer is a type of software developer who specializes in mobile technology. Mobile developers might build apps for Android, iOS, or Windows Phone. These types of developers can also be titled Android or iOS developers. 

The skills you’ll be looking for depend on the role you’re hiring. iOS developers should know how to use Swift, as it's the primary language that's used in iOS app development. Android developers should instead know Java.

But how do you identify the best Android and iOS developers? That's what we'll look at next.

Beginner mobile developer interview questions

What are the top junior mobile developer interview questions? Here you go: 

1. What is Android? 


Android is an open-sourced operating system that’s used on mobile devices (mobile phones and tablets). Android apps execute within their own process and their own instance of Dalvik Virtual Machine(DVM) and Android RunTime(ART).  

2. Explain the Android architecture. 


The Android architecture includes the different layers in the Android stack. Each of these layers supports the layer above it and they include the middleware, applications, and operating systems. The five layers are:

  • Libraries: The Android architecture includes libraries with the open-source web browser engine WebKit, that are used to play and record audio and video, with SQLite database, SSL, and more. 

  • Linux Kernel: Linux Kernel manages device drivers, memory, power, and device management, as well as resource access. 

  • Android Runtime: Dalvik Virtual Machine(DVM) and Android RunTime(ART) are helpful for mobile devices, to provide fast performance while needing less memory, and to execute android apps from Android lollipop 5.o (API level 21). 

  • Android Framework: The Android Framework consists of APIs like UI, content providers, telephony, package managers, and resources. 

  • Android Applications: Android applications (home, games, contact, and so on) use the Android Framework, which makes use of Android runtime and libraries. 

3. What are the advantages of Swift?


Swift is a strongly typed language and it allows protocols, generics, and optionals to exist and aid in development. Thanks to being a statically typed language, it allows for a lot of compile-time warnings and compilation errors. However, that also means greater runtime safety and determinism. 

Swift is especially beneficial when strict explicitness is needed (rather than dynamism and flexibility) or when you need to refactor your code and the compiler works as an aid to writing the code properly and correctly. 

4. What does the iOS architecture look like?


The iOS architecture has a layered structure with four lawyers. Lower-level layers provide services for all applications, while upper-level lawyers provide graphics and interface-related services. The layers are:

  • Core OS Layer: The Core OS Layer is the bottom layer of the iOS stack and it’s positioned directly on top of the device hardware. It offers basic OS services (file system handling, memory management, and so on), but also low-level networking.

  • Service Layer: The Service Layer designs the services that the upper layers and users want. For instance, its essential features include block objects, Grand Central Dispatch, in-app purchases, and iCloud storage. 

  • Media Layer: The Media Layer handles media (video, audio, graphics, and so on). 

  • Cocoa Touch Layer: The Cocoa Touch Layer or the application layer is the place where frameworks are created when applications are built. It’s the interface for iOS users to work with the operating system. 

5. Explain internationalization and localization.


Internationalization is the process of changing app code to other languages to adjust data that might be shown in different ways. Especially prices, numbers, and data formats can vary, as well as how text is written. 

Localization, on the other hand, is all about translating content so that it’s available in different languages. Resources for different languages are often kept in different files and folders and the operating system chooses the right one based on user settings. 

6. What are the best crash and usage reporting tools for released apps? 


One of the most popular ones is Firebase Crashlytics. This app supports both iOS and Android and provides information about app crashes, including the operating system version, device manufacturer, user language, and full-stack trace. Other tools are Sentry, Appsee, and Instabug. 

Advanced mobile developer interview questions

What are the top senior mobile developer interview questions? Here are our top picks: 

7. Explain app sandboxing. 


App sandboxing refers to a security mechanism. Every app runs in its individual sandbox with limited access to data, except for the app’s own data and files. Apps can share some data but only using mechanisms provided by the system. The idea behind this is to protect user data from malicious software. 

8. Describe a ThreadPool. 


A ThreadPool is a software design pattern that maintains multiple threads waiting for tasks to be allocated for concurrent execution. A ThreadPool can run multiple parallel instances of a task because it consists of a task queue and a group of worker threads. 

Using ThreadPool can be more efficient than having multiple operations waiting to run on a single thread. Plus, it can also help you make tasks simpler as you don’t need to create and destroy a thread every time you require a worker thread. 

9. When is a Fragment the best choice rather than an Activity?


There is some debate regarding this topic. However, the code used to create an Activity is much more involved than the code used to create a Fragment, so the new Activity has to be created and the old Activity has to be destroyed, paused, or stopped. Fragments should generally be used and Activities should only be used when you’re swapping the entire screen. 

Over to you!

There you have it! Now you know what the top mobile developer interview questions are.

These questions will help you identify the right candidates. 

But apart from your interviews, you also need to assess candidates’ technical skills.

That’s what CodeSubmit can help you with thanks to our technical skill assessments and live coding interview tools. 

Want to learn more? 

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